A Study on Shock Absorption Characteristics of Honeycomb-inserted Bollards

Lack of shock absorption capability of conventional steel bollards causes significant vehicle damage and consequently high repair costs. This research studies a solution to reduce vehicle damage by inserting PLA honeycomb structures. A honeycomb-inserted bollard was designed based on numerical simulations using LS-DYNA, which yielded the bollard designed for actual vehicle-bollard collision experiments. Simulation efforts were focused on calculating the acceleration characteristics when a vehicle collides with steel and honeycomb-inserted bollards. Compared to the simulated steel bollards, 20 MPa yield-strength honeycomb-inserted bollard showed 0.017s delay in the maximum acceleration occurrence time, reduction of the maximum acceleration to 37.4% of that of steel bollards, and 13.1% reduction in the B-pillar maximum acceleration. Actual vehicle-bollard collision experiments, with a gyro-sensor installed at the test vehicle front bumper frame, also proved improved shock absorption characteristics of the honeycomb-inserted bollards. An experiment with honeycomb-inserted bollard showed 0.783s delay in the maximum acceleration occurrence time, a significant delay when compared to steel bollards. The maximum acceleration measured by the gyro-sensor was 0.35m/s2 when the simulation predicted it to be 0.388 m/s2, proving the similarity in the simulations and experiments. Thus, this study of shock absorption characteristics promised reduced damage to vehicles and lower repair cost.